Wow, I've had this happen, but usually a reboot cures it. By reboot, you're doing a complete shutdown and a cold start? If not, give that a try. Wait until it's fully powered down.

I like rollis13's suggestion of trying to open it in one of the open-source programs. I would also be curious as to whether you're first opening Excel, and then selecting and opening the file from within Excel, or clicking on the file in File Explorer.

I would also suggest running the repair on Excel/Office in "Add or remove programs." We're on Office 365 and I've had to do this a few times. We also had an issue for a while from our IT guy installing 365 and not removing the old Office. Files would open if accessed from within the program, but when double clicked in File Explorer or on the desktop, they would appear to open but be invisible. Eliminating the other Office and running a repair cured this. You might right-mouse-click on your file and check out what your computer is offering under the open-ended "Open With..." line.

I also had a problem after I tried to open an old WordPerfect file in Word. Apparently it tried unsuccessfully to load it and messed things up until I ran the repair. So is it possible you opened something non-Excel in Excel recently?

Hope you are able to figure it out!

Best regards,

Ann